// Show off your Colors
- Water-based coatings and varnishes are a mixture of the several main components (including water, pigment, resin, amines, and performance enhancing additives)
- Water-based coatings at a pH between 8.5 - 9,5 will print and perform optimally
- The rate of evaporation of the amines increases as the coating temperature rises
- Stable water-based coating chemistry = controlled viscosity, stable temperature and optimal density of the coating
- Industry coating consumption studies reveal that a 1-second (Zahn cup) change in coating viscosity can produce a change in coating laydown of up to 50%.
// What happens to the printing process with a water-based coating that is maintained out-of specification?
(1) Coatings with a pH less than 8.5
The integrity of the coating formula is compromised. The stability of the coating is weakening, sludge-like deposits can be noticed in the bottom of the coating pail, the aniloxes will start to clog, plates will start to dirty, printing defects occur more often.
Ø Stoppages every 1500–2000 sheets/hour to clean the plates, wasting about 15 minutes of valuable printing time each time.
(2) Coatings with a pH between 8.5 to 9.5
This guarantees the optimal balance of all the ingredients confirming the water to amines ratio is within specifica-tion. The coating will dry where it should not on the printing plates or in the aniloxes. Optimum performance and efficiency of the printing process is achieved.
Ø With this optimal chemistry, coatings can print 5000–6000 sheets/hour without stopping for plate or anilox cleaning all the while producing exceptional quality product.
(3) Coatings with a pH higher than 9.5
The coating viscosity will be too low. Coating drying on the plates and aniloxes occurs. The dry film thickness is lower, poor print quality (runny), poor color density becomes apparent, ink emulsion problems are possible, trapping problems arise.
Ø Duo-Technik’s Color Management system can liberate a huge amount of “free” press time, improving the print press efficiency, creating lower overall costs while stabilizing the printing process and improving the delivered print quality.